The present invention relates to a composite magnetic body applied in an electronic device for suppressing electromagnetic interference.
In electronic devices, interference due to electromagnetic waves from the exterior or interference given to external devices due to electromagnetic waves radiated from the subject device, that is, so-called electromagnetic interference becomes a problem. This electromagnetic interference problem becomes more significant following use of the higher frequency and reduction in size and power of electronic devices.
For suppressing such electromagnetic interference, electromagnetic shielding by a conductor plate has been conventionally used. However, there is a problem that although the conductor plate blocks transmittance of the electromagnetic waves, it induces secondary radiation due to reflection. Specifically, although it protects an electronic device from electromagnetic waves from the exterior of the device, the secondary radiation due to the reflection influences the external devices. Further, it reflects electromagnetic waves from the inside of the device toward the inside of the device so that other electronic components in the same device are adversely affected. In addition, since components of such undesired electromagnetic waves extend over a wide frequency range, particularly in high frequency devices, there are not a few cases wherein it is difficult to even identify frequency components relating to the electromagnetic interference.
Accordingly, for suppressing the foregoing electromagnetic interference, such a material is desired that absorbs undesired electromagnetic waves over the wide frequencies.
As a material satisfying such a request, JP-A-7-212079 offers a composite magnetic body in which soft magnetic powder having a shape anisotropy is dispersed into an organic binding agent. This composite magnetic body utilizes, for absorption of the electromagnetic waves, magnetic losses over several ten MHz to several GHz which are considered to appear due to a plurality of magnetic resonances of the soft magnetic powder.
The foregoing JP-A-7-212079 discloses an electromagnetic interference suppressing body wherein the composite magnetic body and a conductor are stacked with each other so that transmittance of the electromagnetic waves is blocked by the conductor layer while the electromagnetic waves are absorbed by the composite magnetic body, thereby preventing invasion and reflection of the electromagnetic waves.
On the other hand, in recent years, demands have become stronger relative to many industrial products that they produce no harmful substances and are completely decomposed spontaneously to leave no residue when disposed of, or they have high recyclability. However, the foregoing electromagnetic interference suppressing body or composite magnetic body being a material thereof pays no consideration to such demands.
The present invention has been made for solving such problems and provides a composite magnetic body which can ensure safety upon disposal thereof, can be spontaneously decomposed and has high recyclability, and an electromagnetic interference suppressing body using it.
The present invention, as recited in the claims provides a composite magnetic body comprising flat soft magnetic powder dispersed in an organic binding agent, which is characterized in that the organic binding agent is biodegradable plastic.
Various embodiments of the composite magnetic body according to the present invention are recited in various dependent claims.
Further, the present invention, as recited in claim 4, provides an electromagnetic interference suppressing body comprising the foregoing composite magnetic body and a conductive material.